Oil well drill bit



Dec. 26, 1944. w CRAKE 7 2,365,941

OIL WELL DRILL BIT Filed Aug. 31, 1942 Fig. 13:

Inventor Wilfred 5T.Maur Elmore CraKe Patented Dec. 26, 1944 "2,365,341 o1L #WELL mum-531T Wilfred St." Maur" Elmore Gr'ake, HoustonfTex;

" "assignor to ShellfDevelopment Gompany; San

Francisco; 'Calif.,-a' corporation of Delaware .eap licationn usesi, 194,2, serial No. 455,329

:LfEheapresent: invention: relates tosimprovements uotaryidrilling rbits, 'wandmpertain's-r more :par- --ticularlyr to'wanz. oil twell= bit "for drilling inrrelalftiVBlY;lSDft'fOImatiOHS.

eAsggeneral obj ect: of; this inventionsis tog'provide don-use in drilling wells.

2 Another, object .of .this inventioni'is. towproyide eta-drill: bit; having :its. blades formedxalong-substanz tiallyi hyperbolic-spiral lines. ,LThiS shape: has

aaypractical, efiective and:longewearingedrillsbit .ibeen found to: give :the: greatest cuttinguedge elengthw for: a; given: axial length i and diameter of ebitaand thus .keepsLthe bit shorter forthepa sam AGffEGtIVBEIEQgthOf cutting edge.

:In. the; drillingoi; deep::wells,:.the. bitisi secured 13130 thewlower end :of *azdrilling. string made :up rlofta largesnumberi of. pipe se ctions;.and the string rotatedriand fedpdownwardlyvso thatthe:bit drills away i the earth formation. The cutting parts. or. edges. of .a conventional rotary drag-type a;

l'ortfishtail bitwear away. very: rapidly, and :the

bit must be removed from the well forreplaceamentl-by anew. or reconditioned tool afterza rela- ..tivelyz short; period: of :use. I The removal of: the mom: bit necessitates the withdrawal .and disconmection of the long: string, of drill pipe; :whi'chimust then be lagainrreeassembledi and .lowered into the "well, whereby large time 'lossesxare incurred. '-;'I;he presentimproved bit;:with hyperbolicspiral; blades rhas a .much. longer effective life; than conventional hits, since, due to thelinespf-curvature lusedgthewutting edgesottheibitxarecaused to I wlength. The time-rand labor. lost "in' pulling and stunning;- in: the. drilling string "when ..u'singthe rpresent-bit are accordingly;substantially. reduced.

. ..-*Another object 1 of: this invention .is to prolvide lanriinproved, drill bit: formed :with high. grade l steel blades. of constant. cross-section 'in a lateral -.,or;: radial direction, wherebyza constant 1, pressure won the q bit kWill causex-aa constant 2 unit; loading llbetweenw the fformation-zand the cutting-edge of .the. zblades. until the :out. I

A further object of this inventionrisxto provide a drill bit having upwardly directedzcirculation zportsizlocatedtalong lthellength of the blades,

iTrOmLL-the natural direction-of the cuttingsnas .theyclear the cutting edge of theblades. ':1T=his delays the removal of the cuttings from the bladesgand causes turbulence before the cuttings and circulation fluid; start to move clear of thexbit tasrrequired: for disposal to thesurfacejalong the l outside ofythezdrill pipe. The upwardly-directed tcirculation; portsin the present .drill :bit most :ueffectively maintain the blades free from-cuttings rand muck.

--A'still further object of this invention ,;is- ;to

providewan improvedsdrill bit which has even blades are completelywvorn bearing points-conthe-borehole twalls, -will-.-be smooth; running, iandi will tend to :center 1 itself and to drill straightholes.

With the above and-other objects rinaview, ,;the invention .hasparticular; relation to certainmovel 1. features of construction and arrangement. of parts; an exampleof which is; given in this specifizcationwand is illustrated. by :the accompanying .drawing,, wherein: p

Figure. I is an elevation viewof a preferred .em- .ebodimentlofthe drill bit of thepresent invention. Figure: II is a plan view of an inverteddrill bit. rFigureIIIisa cross-sectionview-taken along the line III..III in-Figure I.

.tiFigure? IV is a cross-section view. taken along :thelineIV-IV.in Figure,I.

Figure 1- V isran elevation view of another-em- :bodiment oi the drill-bit.

Figure VI is'an, elevation view ofistill another embodiment .of the drill bit.

.j.--Figure;VII1is a cross-sectionalview taken along the line. VII--,VII. in Figure VI.

'rReferring totheFigures I toIV; of the=dravving, .agpreferredz embodiment of the ,drill"bit;,of the "present invention is provided with a shank} l0 .xwhich is; illustrated as, a sleeve, having. internal threads l |;1to.engage; the end of. the drill string. It is-to'be understood that; the shank, instead of' being an- -:internally threadedsleeve, canube :aan" externally threadedzcylinder.

.The'body portion of the bit is formed, as shown zin thedrawing, with a plurality, preferably two or: :more, :of; blade-carrying; raised portions 13 zspirally. extending upwardly and outwardly ,from

the apex [2 of. thebit towards the shank 10K in Ta clockwise direction. :In other words, the raised tzportions l3 spiral downwardly and inwardly from .;the shank 10in the direction of rotationuoffthe .bit arid meetornearly meet at the apex l2. .The :blade-carrying: raised portions [3 of the bit; are iso: contoured that the rotation of the bit 1 drills 2a :holehaving a shape substantially like theifigure 55 of?revolution describeck-by ahyperbolaswhemrotated about its focal axis. In other words, the raised portions I3 are contoured in the form of a hyperboloidal or substantially hyperboloidal spiral, that is, spirals on a hyperboloidal base, which figure is obtained by rotating a hyperbola or reasonable modification thereof, about its focal axis. It is preferable that the raised portions I3 converge from the hyperboloidal shape in the lower part of the bit to a cylindrical shape for several inches of vertical length in the upper part of the bit, this upper part thereby constituting a reaming section to maintain full gauge of the drilled hole.

ing portions I3 dip sharply as at I6 ahead of the raised portions I3 in the direction of rotation and then smoothly build up to the preceding raised portions I3. Thus, each face I4 comprises a relatively long inwardly receding portion and a relatively short outwardly and sharply inclined portion I6 arranged with the latter portion IS on the leading or forward side of the raised portions I3, as shown in Figures III and IV.

The blade-carrying raised portions I3 may be integrally formed with cutting edges or blades or, as shown in Figures 111 and IV, preferably, may be fitted with short constant cross-section blades I 8. The cutting edges, whether formed integrally with or inserted into the raised portions I3, are preferably made of high-grade hardened steel, or hard-surfaced. Tool steels, such as tungsten carbide and alloys, such as the chromium-cobalt alloys known as Stellite, may be used.

By constant cross-section blades it is meant that the blades I8 are formed to give a transverse cross-section in the shape of a parallelogram or rectangle, that is, a transverse cross-section with the lateral sides parallel, whereby the thickness of the blade I8 remains constant as it is worn away. The blades I8 are preferably inserted and fastened, such as by welding, into a groove I9 in the peak of the raised portions I3. In order to give a slightly slicing action to the cutting, the blades I8 are preferably set at a leading angle, such as about 10 to 30, for example to a radial line. i. e., a line passing through the axis of the bit and normal or perpendicular to the As shown most clearly in Figure III, the faces I4 between the raised blade-carryable nozzles positioned along the leading side of the blades I8. If desired, the axial bore 24 extending through the shank III into the drill bit body may be tapered or, as shown by dotted lines in Figure I, may be in the form of a hyperbolic figure of rotation similar'to the outer general shape of the bit.

It will be readily seen that in operation the improved drill bit of thepresent invention provides numerous advantages over prior bits. The hyperboloidal spiral contour of the blades I8 gives a long wearing bit and provides the greatest cutting length per vertical length and per unit diameter of the bit, thus keeping the bit shorter for the same effective length of cutting edge or blade. In addition, the rotating action of the bit causes the spiral blades I8 to act as a screw pump impeller and to assist in forcing or pumping outtings and circulating mud or drilling fluid upwardly to clear the bit. Further this type of blade will require less horsepower and torque to rotate and thus will give steadier and smoother cutting action. The form and position of the upwardlydirected circulation ports 23 causes the fluid, such as mud, circulation to be directed so that cuttings are forced in the natural direction of flow from the cutting edge of the blades I8 to clear the bit,

, made of the available circulation of drilling fluid.

formation. This arrangement in addition gives greater life to the cutting edge of theblades I8.

At the juncture of the sharply inclined portions I6 and the long receding portions of the faces I4 between the blade-carrying raised portions I3, that is, closely adjacent to and onthe upper side of the blades I8, are a series of streamlined bulges 2| having flat faces 22 in more or less perpendicular relation to the blades I8 adjacent thereto. Arcuate bores or ports 23 extending from said faces 22 through the bulges 2I to the axial bore 24 in the bit body serve as fluid circulation channels, or water-courses, through which drilling fluid or mud, or the like, is discharged in an upward direction along the sharply-inclined faces I6 of the raised portions I3 and the upper and leading side of the blades I8, whereby the blades I8 are kept washed clean by a smoothly flowing upwardly-swirling stream of drilling fluid issuing from said ports 23. Preferably, as shown in Figure I, the bulges 2| and their circulation ports 23 are spaced along adjacent each raised portion I3 with one close to the apex or tip I2 of the bit and two, as shown, or more, up further on the bit. The bottom holes 23a point downwardly, but at an angle which causes the fluid therefrom to start flowing along the edge of the blade. 'On the other hand, the mud ports may be formed of remov- Various modifications and changes may be made within the scope of the appended claims without departing from the spirit of the invention. Thus, although the above-described hyperboloidal spiral-bladed drill bit is the preferred form of the invention, some of the advantages of the present invention are retained with a hyperboloidal drill bit having non-spiral blades, as shown in Figure V, or with a flat bottom drill bit having spiral blades, as shown in Figures VI and VII.

Referring to Figure V, the second embodiment of the drill bit comprises a shank I0 having ini ternal threads II, a hollow body 50 of substantially hyperboloidal shape, axial blades 5I projecting from said body 50 and preferably meeting at the apex 52 at the bottom of the bit, and preferably streamline bulges 53 on the leading side of said blades 5| and having upwardly-directed mud ports 54 therein.

Referring to Figures VI and VII, the third embodiment comprises a cylindrical bit body having internal threads 6| at its upper end, the lower end of the body 60 being rounded ofi, and blades 82 projecting from said body 60. The blades 62 in transverse cross-section, as shown in Figure VI, have a form spiralling outwardly in the direction of the rotation of the bit, with the outer end of the inner face modified slightly to a substantially straight portion 65. Vertically the blades 62 are parallel to the axis except for the lower portions 63, which are slightly tapered, as shown in Figure VII. Ports 84 provide passage of drilling fluid from within the axial bore 65 of the drill.

I claim as my invention:

1. An improved drill bit for rotary drilling of wells comprising a hollow body having a plurality of laterally-extending cutting edges curved splrally downwardly in the direction of rotation of the drill bit and substantially meeting at an apex at the lower end of the bit said cutting edges together with said hollow body being formed to describe upon rotation of the bit a substantially hyperboloidal figure of revolution, said body' having fluid circulation ports extending therethrough and directed upwardly adjacent said spiral cutting edges on the leading side of said cutting edges, and means in the upper end of said hollow body for connecting the bit to a drill string.

2. An improved drill bit for rotary drilling of wells comprising a hollow body formed with a plurality of laterally raised portions curved spirally downwardly in the direction of rotation of the bit and substantially meeting at an apex at the lower end of the bit, each of said raised 'portions having a groove along its peak, cutting edges comprising blades partially inserted and fastened in said grooves at a leading angle of 10 to 30 to a radial line from the axis of the bit, said blades having a transverse cross-section substantially in'the form of a parallelogram, passage means through said hollow body for conducting and directing circulation fluid against the forward side of said cutting edges, and means in the upper end of said hollow body for connecting the bit to a drill string.

3. An improved drill bit for rotary drilling of wells comprising a hollow body formed with a plurality of raised portions curved spirally downwardly in the direction of rotation of the bit and substantially meeting at an apex at the lower end of the bit, each face between pairs of raised portions on said body being formed with a relatively long inwardly-receding portion and a relatively short outwardly and sharply inclined portion arranged with said sharply inclined portion adjacent the leading side of said raised portions, said raised portions having formation cutting edges, said raised portions and said cutting edges together with said hollow body being formed to describe upon rotation of the bit a substantially hyperboloidal figure of revolution, passage means through said hollow body for conducting and directing circulation fluid againstthe forward side of the cutting edges, and means in the upper end of said hollow body for connecting the bit to a drill string.

4. An improved drill bit for rotary drilling of wells comprising a hollow body formed with a plurality of raised portions curved spirally downwardly in the direction of rotation of the bit and substantially meeting at an apex at the lower end of the bit, each face between pairs of raised portions on said body being formed with a relativelylong inwardly-receding portion and a relatively short outwardly and sharply inclined portion arranged with said sharply inclined portion adjacent the leading sides of said raised portions, streamlined bulges spaced along the junctures of said receding and sharply inclined portions of the faces between the raised portions, each of said raised portions having a groove along'its peak, cutting edges comprising blades of hardened steel partially inserted and fastened in said grooves at an angle of 10 to 30 to a radial line of the bit, said blades having a transverse crosssection substantially in the form of a parallelogram, said raised portions and cutting edges together with said hollow body being formed to describe upon rotation of the bit a substantially hyperboloidal figure of revolution, passage means extending through the walls of said hollow body and said bulges, the outlet opening of said passages in said bulges being directed upwardly along the leading side of the cutting edges, and means in the upper end of said hollow body for connecting the bit to a drill string.

WILFRED ST. MAUR ELMORE CRAKE. 

